Hydraulic cylinder assembly



De- 26, 1967 R. l.. HOFFMAN ETAL 3,359,868

HYDRAULIC CYLINDER ASSEMBLY 4 Sheets-Sheet l Filed April 8, 1965 @NN NNNW @lm Mm WFM De 26, 1967 R. L.. HOFFMAN r-:TAL 3,359,868

HYDRAULIC CYLINDER ASSEMBLY- Filed`April 8, 1965 4 Sheets-Sheet 2 DC- 261967 R. L. HOFFMAN ETAL 3,359,868

HYDRAULIC CYLINDER ASSEMBLY Filed April s, 1965 K 4 sheets-sheet s DeC-25, 1967 R. l.. HOFFMAN ETAL. 3,359,858

HYDRAULIC CYLINDER ASSEMBLY Filec April 8, 1965 4 Sheets-Sheet 4 QQ y///2.97 v 2,67 365 *@5- 556 f5! a y United States Patent O 3,359,868HYDRAULIC CYLiNDER ASSEMBLY Robert L. Hoifman, St. Joseph, and Robert C.Miller and John T. Parrett, Benton Harbor, Mich., assignors to BentonHarbor Engineering Works, Incorporated, a corporation o Michigan FiledApr. 8, 1965, Ser. No. 446,654 14 Claims. (Cl. 91-447) ABSTRACT F THEDISCLSURE A holding valve for selectively prevented discharge flow froma hydraulic motor, the valve being biased to a closed position againstthe force of fluid tending to discharge from one side of the motor witha uid operable device for opening the valve permitting discharge fromone side of the motor when uidis ported to the other side of the motor.

This invention relates to the control of reciprocating hydraulic motorsand more particularly to a holding valve for controlling the flow ofliuid relative to a hydraulic cylinder.

In hydraulic systems where a reciprocating hydraulic motor is employedto raise and lower a movable load, a directional control valve isconventionally employed to selectively port fluid to and from thehydraulic motor. In such devices the directional control valve ismovable to a block position to prevent discharge ow from either end ofthe hydraulic motor to thereby attempt to hold the load stationary.However, the force of gravity acting on the load produces an increasedpressure `in one end of the cylinder which causes fluid to leak aroundthe directional control valve resulting in load creepage.

Counterbalance holding valves have been provided in the past in anattempt to obviate this creepage problem. These prior Valves have beeninterposed in the hydraulic circuit between the hydraulic cylinder andthe directional control valve to selectively prevent flow from thecylinder when the directional control valve is in the 'block position.These holding valves must also be capable of permitting fluid liow fromone side of the cylinder when the directional control valve ports driveuid to the other side thereof. For this purpose the holding valve isoverridden usually by means of a pressure responsive actuator locatedbetween the hydraulic cylinder and the holding valve.

The serious disadvantage of these prior valves is that they have beendependent for their holding ability upon the integrity of certainpackings or seals used in their construction. Since these packings andseals have a relatively short life, they have proved a detriment in theuse of these valves and in some cases have been a negative factor from asafety standpoint.

It is therefore a primary object of the persent invention to provide anew and improved holding valve assembly for la hydraulic motor in whichthe valve has a holding ability far superior to any heretofore knownvalves. In the present device the holding ability of the valve isdependent entirely on the metal-to-metal contact between the valve seatsthereby minimizing the possibility of leakage.

It is another object of the present invention to provide a new andimproved counterbalance holding valve for a hydraulic cylinder includinga piston formed on the movable valve member which is responsive to inletiiuid pressure to selectively open the holding valve. This actuatorpiston is on the low pressure side of the system when the associateddirectional control valve is in the block posi- 'tion so that anyleakage will take place on the reservoir` ice side of the system and noton the hydraulic cylinder side thereby preventing load creepage.

A further object of the present invention is to provide a new andimproved holding valve of the type described above including a strongcompression spring for biasing the holding valve to its closed positionin opposition to the force of the liuid on the valve from the hydrauliccylinder.

A still -further object of the present invention -is to provide a newand improved holding valve construction of the type described abovecapable of holding the hydraulic motor from movement in eitherdirection.

Another object of the present invention is to provide a new and improvedholding valve construction of the type described above including a valveplate for enclosing said holding valve structure, and a bypass passagehaving a check valve therein permitting iluid ow to the hydrauliccylinder but preventing tlow in the reverse direction.

Another object of the present invention is to provide a new and improvedholding valve construction of the type described above in which thebypass passage and the check valve are an integral part of the movableholding valve member. In one embodiment the bypass check valve is of theball type and in another embodiment the check valve is of the plungertype extending completely through the movable valve member.

Still another object of the present invention is to provide a new andimproved hydraulic cylinder assembly including a holding valveconstruction of the type described above in which the holding valveincludes a v-alve plate mounted on one end of a main piston rodconsisting of concentric sleeves. The spaces within the sleeves definethe fluid flow conduits to both sides of the main piston within thehydraulic motor cylinder thereby providing a simplified construction notheretofore known in the art.

Other objects and advantages will be apparent from the followingdetailed description, taken in connection with the accompanying drawingsin which:

FIG. l is an elevational view partially in cross section showing thehydraulic cylinder assembly;

FIG. 2 is a sectional view taken generally along line 2 2 of FIG. lshowing the counterbalance holding valve assembly;

FIG. 3 is an elevational view, partially in cross section, showinganother embodiment of the hydraulic cylinder assembly in which theholding valve .assembly is connected to the piston rod;

FIG. 4 is a sectional View taken generally along line 4-4 of FIG. 3showing `another form of the holding valve assembly;

FIG. 5 is a cross section taken generally along line 5-5 of FIG. 4showing the fluid passages which connect the main piston rod with theholding valve assembly;

FIG. 6 is a cross section taken generally along line 6 6 of FIG. 5showing one of the holding valve bores;

FIG. 7 is a cross section of another embodiment of the holding valveassembly;

FIG. 8 is a fragmentary cross section of still another embodiment of theholding valve; and

FIIG. 9 is a cross section of another ambodiment of the holding valveassembly.

Referring to FIG. 1, the hydraulic piston and cylinder assembly 10includes a reciprocating piston 11, a cylinder 12, and a holding valveassembly 13 iixed to the stationary cylinder 12. A pivot mount 15 isadapted to be pivotally mounted on a suitable pin on a relativelystationary portion of a lifting device (not shown) associated with thehydraulic cylinder 10. Another pivot mounting 16 is adapted to beconnected through another pin to the load. As fluid is selectivelyported to either side of the piston 11, the mount 16 will extend andretract with respect to the cylinder 12.

More specically, the cylinder 12 has cylindrical outside and insidesurfaces with one end threaded as at 18 to receive a suitable end capand seal assembly 19 which slidably receives piston rod 20.

The holding valve assembly 13 includes a rectangular valve plate 21 withan annular projection 22 on one side thereof which ts within the rightend of cylinder 12. The holding valve assembly 13 is suitably welded asshown at 24 to the cylinder 12. The piston rod 20 has a reduced endportion 26 received within the piston 11 with a threaded portion 27threadedly receiving a piston cap 28 which functions to maintain thepiston assembly 11 on the reduced piston rod portion 26.

The piston 11 devides the cylinder 12 into chamber 31 and chamber 32.Fluid is ported to and from chamber 32 through passage 33 in the holdingvalve assembly 13. Fluid is ported to and from chamber 31 through asuitable conduit 35 which communicates with a port 36 in the cylinder 12and with the holding valve plate 21 in a manner more fully describedbelow.

Turning now to the detailed construction of the holding valve assembly13 as shown in FIG. 2, inlet ports 40 and -41 are provided both of whichfunction to convey supply and discharge fluid between a directionalcontrol valve (not shown) and the hydraulic cylinder 12. Port 40supplies and returns iluid to and from hydraulic cylinder chamber 31while port 41 supplies and returns fluid to and from hydraulic chamber32. Port 40 communicates with the hydraulic cylinder chamber 31, whenpressurized by the directional control valve, through passages 43, 44and 45, and through a poppet valve 46 slidably mounted with clearance inIbore 47. Poppet valve 46 permits flow from passage 44 to passage 45 butprevents tiow in the reverse direction. Spring 4S seated against plug 49threaded in bore 47 urges the poppet valve 46 to its closed position. Asim-ilar inlet liuid circuit is provided associated with port 41including passages 50, 51 and 52, the latter communicating with passage33 opening to hydraulic cylinder chamber 32. A poppet bypass valve 54 isidentical in construction to poppet valve 46 and permits flow frompassage 51 to passage 52 but prevents flow in the reverese direction.

Holding valves 56 and 57 are provided in the valve plate 21 forselectively preventing tluid ow from the hydraulic cylinder chambers 31and 32 to the ports 40 and 41. The holding valves 56 and 57 are of thecounterbalance type in that they are biased in opposition to fluidpressure in the hydraulic cylinder chambers. Holding valve 56 preventsthe ow of iluid from chamber 31 and holding valve 57 prevents the ow offluid from chamber 32. The holding valves 56 and 57 are identical inconstruction and for this reason the details thereof will be describedwith reference only to holding valve 56.

The holding valve 56 includes a stepped bore 60 which intersects thepassage 44 and a discharge passage 62 which communicates with conduit 35through a suitable tting 64.

A movable valve member 65 is slidably received in the stepped bore 60.Valve member 65 has a conical valve surface 66, a reduced portion 67, acentral piston 68 and an end piston 69. An axial bore 70 is formed inthe valve member 65 which communicates with radial passages 71 openingto the reduced portion 67. The reduced portion 67 denes a chamber 74 inbore 60. Pistons 68 and 69 deline a chamber 75 in bore 60 which togetherconstitute a differential piston mechanism for operating the valve in amanner described below. Restricted passages 77 and 78 meter fluid frompassages 43 and 50, respectively, to the chambers 75 between thedifferential pistons. As the area of piston 69 is greater than that ofpiston 68 within chamlber 75 the iluid metered into chambers 75 movesthe valve members to their open positions.

A counterbalance spring 80 is provided for biasing the valve member 65to its closed position wherein the conical valving surface 66 tightlyengages circular edge valve seat 81 in the right end of bore 60. Thespring 80 is of the coil with the seat 81 against the force of uidtending to discharge through passage 62 and acting against the right end83 of the valve member 65. This discharge flow tendency is created bythe load when the associated directional control valve is in its blockposition. Spring 80, mounted within the bore 60, engages the large endof the valve member 65 and reacts against a plunger 85 slidably mountedin a hollow hexagonal cap 86 threaded into bore 60. An adjusting screw87 threaded into cap 86 abouts the end of the plunger 85 and permitsadjustment of the plunger 85 to vary the compressive force of spring 80on valve member 65. A suitable locking nut 88 is provided for screw 87.

Counterbalance valve 57 is provided with a discharge passage 91 in valveplate 21 which communicates with passages 52 and 33, thereby providingthe same function as the discharge passage 62 provides with respect toholding valve 56.

In an exemplary operation of the FIGS. l and 2 embodiment, assume thatthe directional control valve is positioned so that port 41 is connectedto a suitable source of supply tluid and that port 40 is connected tothe reservoir. High pressure fluid flows through passages 50 and 51opening poppet valve 54 permitting fluid to ow through passages 52 and33 into the hydraulic cylinder chamber 32. At the same time a smallportion of this fluid in passage 51 is metered thro-ugh the restrictedorifice 78 to the ditierential piston chamber 75 in valve 56. The valvemember 65 then moves to the left in bore 60 to its open position againstthe force of spring With holding valve 56 open, discharge ow ispermitted from the hydraulic cylinder chamber 31 through conduit 35,discharge passage 62, chamber 74, passage 43 (then a return passage) andout port 40. The piston 11 then moves to the left as shown in FIG. l.

When it is desired to hold the load connected to pivot mount 16, thedirectional control valve is placed in its blocking position preventingfluid ow to or from either of the ports 4t) or 41. In this position thepassages 43, 44, 50 and 51 are under what may be termed low pressure.Because of this the pressure in differential chamber 75 of valve 56drops and the spring 80 moves the valve member 65 to the right to itsclosed position. Both valves 56 and 57 are then in their closedposition. Regardless of the direction of the static load on the pivotmount 16 the holding valves 56 and 57 will prevent any creepage of thepiston 11. If the static load has a tendency to force Huid from chamber31 the pressure in discharge passage 62 will be relatively high but thecompression spring 80 maintains the movable valve member 65 closedpreventmg any leakage.

It should be noted that there are no packings or seals in dischargepassage 62, or the discharge or right end of bore 60, so that leakageand resulting piston creeping is minimized. Any leakage around thedifferential piston does not affect the integrity of the valves holdingability because it is solely on the low pressure or directional controlvalve side of the valve seat 81.

If the directional control valve is reversed so that high pressure fluidis ported to port 4G and the reservoir connected to port 41, theoperation of valves 56 and 57 is reversed. That is, high pressure fluidflows through passages 43 and 44 opening poppet valve 46 permittingliuid to flow through passage 45 and into the hydraulic cylinder chamber31. A portion of this ilow is metered through restricted passage 77opening holding valve 57 in the same manner as that described above withrespect to valve 56. Discharge flow from hydraulic cylinder chamber 32then passes through discharge passage 91, between the open valve seats,passages 51 and 50, and out port 41. Piston 11 then moves to the right.

A second embodiment of the hydraulic piston and cylinder assembly isshown in FIGS. 3, 4, and 6. Hydraulic piston and cylinder assembly 110is generally similar in construction to the embodiment of FIGS. 1 and 2except that the valve assembly is connected to the piston rod and uid isported to the cylinder through the rod. The hydraulic cylinder assembly110 consists generally of a piston 111 slidable relative to a cylinder112 and a holding valve assembly 113 affixed to one end of a piston rod128. Pivot mounting bosses 115, connected to cylinder 112, and trunnions117, also connected to the cylinder, are provided for connection to theload or driven element of the associated machine. Mounting bosses 116form a part of the piston rod 128 and are adapted to be connected to astationary portion of the associated machine. A suitable end cap andseal assembly 119 is provided for the left end of cylinder 112.

The piston rod 120 consists of an outer sleeve member 133 and an innersleeve member 134 threaded at one end in the valve plate 121 and at theother end in piston support 126. The outer sleeve member 120 is weldedat one end to the valve plate and at the other end to the piston support126. Sleeves 133 and 134 define an annular passage 135 and an axialpassage 136. Passage 135 communicates with hydraulic cylinder chamber131 through port 138. Passage 136 communicates with hydraulic cylinderchamber 132 through axial passage 139 in the piston support 126. Passage141 in valve plate 121 communicates with passage 136, while passage 142in valve plate 121 communicates with passage 135.

Referring to FIG. 4 wherein the valve plate assembly 113 for thehydraulic cylinder 110 is shown in detail, holding valves 156 and 157are provided in valve plate 121 and are of identical construction to theholding valves 56 and 5'7 shown in FIG. 2. For this reason the detailsof the valves themselves will not be described in detail. However, thevarious inlet and discharge passages are different though similar infunction and operatio-n. Ports 140 and 141 in valve plate 121 areadapted to be selectively connected to either a source of supply fluidor a drain through a suitable directional control valve (not shown).Each port communicates with the enlarged end of its respective valvebore 160 through passage 168. Passages 170 and 171 in movable valvemembers 165 function in the FIG. 4 embodiment to convey high pressurefluid to the hydraulic cylinder and discharge uid from the hydrauliccylinder. y

When port 140 is pressurized fluid flows through passage 168, bore 160i,passage 170, passage 171, passage 172 and through poppet valve 146 whichpermits flow through passage 142 to the hydraulic cylinder chamber 131.Discharge fluid from chamber 132 then passes through passages 136, 141',182, 183, through the open valve surfaces in holding valve 157 throughthe center of the holding valve, and out port 141.

When port 141 is pressurized and port 140 connected to drain, valve 156opens, and discharge fluid from hydraulic chamber 131 passes throughpassage 135 in piston 120, diagonal passage 174 (shown more clearly inFIGS. 5 and 6), passages 171 and 170, the large end of bore 160, andoutport 140. Pressurized inlet Huid flows at that time through themovable valve member in holding valve 157, passage 180, opening poppetvalve 154 which permits flow through passages 181, 182, 141', 136 and139 into the hydraulic chamber 132. Cylinder 112 then moves tothe rightas shown in FIG. 3.

The operation of the holding valve assembly 113 is otherwise identicalto that of the FIG. 2 embodiment and for this reason will not bedescribed in any further detail.

Referring now to FIG. 7 wherein another embodiment of the holding valveassembly is shown, generally designated by the numeral 213, holdingvalve 213 is functionally similar to the holding valves 13 and 113 butdiffers structurally therefrom primarily in the provision of a combinedcheck and counterbalance valve. Inlet ports 240 and 241 are adapted tobe selectively connected by a directional control valve to either asource of supply fluid or a reservoir. The combined holding and checkvalves 256 and 257 are identical so that the description thereof will bereferenced only to valve 256.

The holding valve 256 includes a stepped bore 260 in valve plate 221with a valve seat 261 at one end thereof. A. valve member 265 isslidably mounted in the bore 260. Valve member 265 includes a valvesurface 266 adapted to engage the valve seat 261 in the bore. Pistons267 and 268 are formed integrally with the valve member 265 and define adifferential piston device. The differential piston is supplied fluidthrough restricted passage 26-9 which connects the port 241 to the valvebore 260 between the pistons. Valve mem-ber 265 has a counterboredspring seat 270 which receives compression spring 280. The valving endof member 265 has intersecting passages 281 and 282 therein with passage281 opening to the forward end of the valve member and defining a valveseat 284 therein. Passage 282 communicates with the interior of bore260.

A check valve assembly 285 is provided for permitting inlet fluid flowfrom port 240 to one side of the associated hydraulic motor butpreventing reverse ow. Check valve 285 includes a ball valve member 286which engages the valve seat 284 to close passage 281. The ball 286 isresiliently biased against seat 284 by spring 287 which reacts against aplug 2,88 threaded into bore 289.

When port 240 is pressurized uid flows through passage 290, passage 282,passage 281, opening check valve 285, which permits iiow into bore 289,and through passage 291 which is connected to one side of the associatedhydraulic motor by suitable fittings (not shown). With port 240pressurized, port 241 is at tank pressure so that the fluid-actuateddifferential piston on valve 256 is not pressurized and the valveremains closed with the valve surface 266 engaging valve seat 261. Atthis time valve 257 is open due to the actuation lof its associateddifferential piston device permitting discharge flow from the other sideof the hydraulic cylinder out through passage 297 and port 241. Whenport 241 is pressurized, the movable valve member 265 opens valvesurfaces 261 and 266 permitting discharge flow from one end of thecylinder through passage 291, over valve surface 266 through passage 290and out port 240. At the same time, motive fluid is supplied to theother end o-f the hydraulic cylinder through passage 295, through checkvalve assembly 296 and passage 297 which is adapted to be connectedthrough suitable fittings to the other side of the hydraulic cylinder.When uid ow in ports 240 and 241 is blocked by the directional controlvalve (not shown) the holding valves 256 and 257 including check valves285 and 296 prevent flow from the hydraulic cylinder through passages291 and 297, respectively.

In FIG. 8, another form of the check or bypass valve is shown designatedby the numeral 385. Valve member 365 is identical to valve member 265 inFIG. 7. Axial passage 381 opens to the forward end of the valve anddefines a check valve seat 384. Axial passage 386 together with passage381 provide a through bore in valve member 365. The check valve 385includes an elongated valve stem 392 slidably received in bore 386 withan enlarged conical head at one end thereof defining a conical valvingsur-face 393 adapted to selectively engage valve seat 384. The other endof stem 392 projects into bore 394 in valve member 365. A springassembly 396 is provided for `biasing the valve stem 392 to the leftinto the valve member as shown in FIG. y8. When passage 390 i-spressurized uid flow in passage 381 acts against valve surface 393urging the stem 392 to the right opening the valve against the opposingforce of spring 396. When passage 390 is at low pressure, the checkvalve closes preventing flow from passage 391 to passage 381. A

The valve assembly 413 shown in FIG. 9 is similar to that shown in FIG.2 except that it is a separate assembly unconnected to the hydrauliccylinder except by suitable tho-sing. For this purpose outlet ports 414and 415 are provided to which the hosing and fittings are connectedlfrom both sides of the associated hydraulic cylinder. Thecounterbalance holding valves 456 and 457 are similar to the FlG. 2holding valves except for certain features. Inlet port 440 communicateswith poppet valve 446 through passage 471, in a similar manner to theFIG. 2 holding valves. lInlet port 441 on the other hand communicateswith poppet valve 454 through bore 460, pa-ssage 470 in valve member 465and chamber 472 in bore 460. Bypass passages 475 and 476 permit highpressure flow through the poppet valves 446 and 454, respectively, tothe respective sides of the associated hydraulic 4cylinder. Dischargepassages 477 and 478 are provided for permitting flow from the hydrauliccylinder when the respective holding valves are open. The operation ofholding valve assembly 413 is otherwise identical to that described withreference to FIG. 2.

Having described our invention as related to the embodiments shown inthe accompanying drawings it is our intention that the invention be notlimited by any of the details of description, unless otherwisespecified, but rather be construed broadly within its spirit and scopeas set out in the accompanying claims.

We claim:

1. A holding valve assembly adapted for use with a hydraulic load,comprising: a valve housing member, a discharge passage in said housingmember adapted to receive discharge flow from the hydraulic load, avalve seat in said passage, a movable valve member in said passage,resilient means for maintaining said valve member in a closed positionin opposition to the force provided by fluid tending to dischargethrough said passage, said valve seat limiting movement of said valvemember beyond said closed position, fluid operable means for selectivelyopening said valve and permitting discharge flow through said passage,and bypass passage means in parallel with said valve membercommunicating with said discharge passage for supplying fluid underpressure to said discharge passage and said hydraulic load.

2. A holding valve assembly adapted for use with a reciprocatinghydraulic piston and cylinder device having an inlet port and adischarge port, comprising: a valve housing member, a discharge passagein said housing adapted to be connected to the cylinder device dischargeport to receive discharge fluid from the device, a valve seat in saidpassage, a valve member in said passage positioned to close inopposition to the pressure of the discharge fluid so that dischargefluid tends to open said valve member, a low pressure return passage insaid valve housing selectively connectable with said discharge passagethrough said valve member, resilient means for biasing said valve memberto a closed position, said resilient means being of sufficient strengthto maintain said valve member closed against the pressure of thedischarge fluid in said discharge passage, said valve seat limitingmovement of said valve member beyond said closed position, control meansfor selectively opening said valve member and permitting discharge flowfrom said discharge passage to .said return passage including fluidactuated means separate from said discharge passage connected to opensaid valve member whereby discharge fluid leakage is minimized andbypass passage means in parallel with said valve member communicatingwith said low pressure return passage and said discharge passage forsupplying fluid under pressure to the discharge port of the device.

3. A holding valve as defined in claim 2 and further including inletpassage means in said housing adapted to be connected to the cylinderdevice inlet port, said control means including a piston means on saidmovable valve member adapted to open said valve in opposition to saidresilient means, passage means connecting said inlet passage means andsaid piston so that fluid flow through said inlet passage actuates thepiston means and opens the valve member.

4. A holding valve as defined in claim 3 wherein said piston meansincludes a piston formed integrally with said movable valve member.

5. A holding valve as defined in claim 2 and further including a valveseat in said valve housing separating said discharge passage and saidreturn passage, said valve member having a valve surface movable withinand engaging said valve seat in the closed position, said resilientmeans maintaining tight engagement between said valve seat and saidvalve surface, said fluid actuated means being connected to said valvemember at the end thereof opposite said valve surface whereby thedischarge passage is separated from said fluid actuated means by thevalve surface and Valve seat to prevent fluid leakage from the dischargepassage.

6. A holding valve as defined in claim 3 and further including a valvebore intersecting said discharge passage, a valve seat in one end ofsaid bore adjacent said discharge passage, said return passage meansintersecting said valve bore adjacent the side of said valve seatopposite said discharge passage, said valve member being slidable insaid bore and having a reduced portion at one end thereof adjacent saidreturn passage, a conical valve surface on said one end of the valvemember selectively engageable within said valve seat, said piston meansincluding a differential piston on the other end of said valve member,said passage means connecting inlet passage to said piston means havinga restricted portion for metering fluid to said differential piston toopen said valve member, said resilient means including a compressionspring in said bore engaging the end of the differential piston, andmeans for adjusting said spring to vary the valve closing force.

7. A counterbalance holding valve assembly for a hydraulic motor havingtwo selectively operable ports for conveying fluid to drive the motor intwo directions, comprising: a valve housing member, two first passagemeans in said housing adapted to selectively communicate with a sourceof supply fluid and a return means, two second passage means in saidhousing adapted to be connected respectively to convey and return fluidto and from the hydraulic motor, check valve means interconnecting eachpair of first and second passages permitting flow from said firstpassage to said second passage but preventing reverse flow, dischargepassage means in said housing by-passing each of said check valve means,a holding valve associated with each discharge passage for selectivelypreventing return flow from the hydraulic motor including a valve seatin such of said discharge passage means, movable valve members eachselectively engageable with one of said seats, resilient means forbiasing each of said valve members into said valve seats and being ofsufficient strength to maintain said valve engagement against the forceof fluid in said discharge passages, and fluid actuated means associatedwith each of said valve members responsive to fluid pressure in thefirst passage a-ssociated with the other valve member for opening saidvalve members and permitting discharge flow through the associateddischarge passage means, said fluid actuated means being separated fromsaid discharge passage means to prevent fluid leakage therefrom.

8. A counterbalance holding valve as defined in claim 7 and furtherincluding two valve bores each intersecting one of said dischargepassage means and one of said first passages, said valve seats beingdisposed in said bores between said discharge passage means and saidfirst passages, said valve members being slidably disposed in said boresand having conical valve surfaces engageable with said seats, said fluidactuated means including differential pistons on each of said valvemembers, restricted passage means connecting each of said first passageswith the respective differential pistons to render the piston responsiveto a predetermined fluid pressure therein.

9. A counterbalance holding valve as defined in claim 7 wherein saidvalves are oppositely disposed so that the fluid actuated meansassociated with each valve is adjacent the valving surface end of theother valve, oppositely extending bores in said housing member forreceiving said valve members, said bores communicating with theassociated first passage means and discharge passage means, andrestricted passages connecting each of said bores between the iluidactuated means and the first passage means.

10. A counterbalance holding valve assembly for a reciprocatinghydraulic motor having inlet and discharge ports, comprising: a valvehousing, first passage means in said housing adapted to be selectivelyconnected to a source of fluid supply and a reservoir, second passagemeans in said housing adapted to be connected to one of said hydraulicmotor ports, a counterbalance valve for porting fluid between said rstand second passage means including a valve bore interconnecting saidfirst and second passage means, a valve seat in said bore, a valvemember slidable in said bore and having a valve surface selectivelyengageable within said valve seat, said passage means in said valvemember continuously communicating with said first passage means andopening to said second passage means, check valve means in said secondpassage means engaging said valve member for selectively closing saidvalve member passage means, said check valve permitting flow throughsaid valve member passage from said rst passage to said second passagebut preventing reverse fiow, resilient means engaging said valve memberfor biasing the valve surface against the valve seat, said resilientmeans being of suicient strength to maintain said valve member closedunder the opposing fluid pressure in the second passage, said valve seatlimiting movement of said valve member beyond the closed position, andiluid actuated means separate from said second passage for opening saidvalve member to permit fluid flow from said second passage to said firstpassage.

11. A counterbalance holding valve assembly as dened in claim 10 whereinsaid bore is a stepped bore, said fluid actuated means including firstand second pistons on one end of said valve member defining adifferential piston, passage means in said housing for metering fluid tosaid differential piston, said resilient means including a compressionspring in said bore engaging one of said pistons.

12. A counterbalance holding valve assembly as defined in claim 10wherein said check valve means includes a ball member in said secondpassage engaging said valve member passage, and spring means in saidsecond passage engaging and biasing said ball member.

13. A counterbalance holding valve assembly as defined in claim 10wherein said valve passage includes an axially extending passagecompletely through said valve member, said check valve means includingan elongated valve stem slidably received in said valve passage, aconical check valve surface on one end of said valve stem projectingfrom one end of said valve passage adjacent said second passage, saidvalve stem projecting from the valve member at the other end thereof,and spring means engaging the projecting stern portion for urging theconical check valve surface to its closed position in engagement withthe valve member passage.

14. A hydraulic cylinder assembly, comprising, a hydraulic actuatorincluding a cylinder and a piston slidable in the cylinder, por-t meansin said actuator for supplying and discharging Huid in said cylinderrelative to one side of said piston, a holding valve assembly forselectively preventing discharge flow from said one side of saidcylinder including valve housing means, a discharge passage in saidhousing means connected to said port means to receive discharge flowtherefrom, a movable valve member in said passage, resilient means formaintaining said valve member closed in opposition t0 the force providedby fluid tending to discharge through said passage, means forselectively opening said valve and permitting discharge flow throughsaid passage, and bypass passage means in parallel with said Valvemember communicating with said discharge passage for supplying fluidunder pressure to said port means and said one side of said piston.

References Cited UNITED STATES PATENTS 1,785,726 12/1930 Balash 137-5412,362,339 11/ 1944 Armington 91-447 2,577,462 12/ 1951 Hackney 92-612,778,598 1/1957 Bolling 251-63 2,797,972 7/1957 Martin 92-111 3,136,2236/1964 Evans et al 91-420 3,150,857 9/1964 Molloy 251-63 3,152,60610/1964 Vedder et al 137-4932 3,168,853 2/1965 Prince 92-110 3,198,0888/1965 Johnson et al 91-447 3,209,781 10/ 1965 Strader 91-420 3,272,0859/ 1966 Hajma 91-447 FOREIGN PATENTS 677,900 8/ 1952 Great Britain.

EDGAR W. GEOGHEGAN, Primary Examiner.

MARTIN P. SCHWADRON, Examiner.

B. L. ADAMS, Assistant Examiner.

2. A HOLDING VALVE ASSEMBLY ADAPTED FOR USE WITH A RECIPROCATINGHYDRAULIC PISTON AND CYLINDER DEVICE HAVING AN INLET PORT AND ADISCHARGE PORT, COMPRISING: A VALVE HOUSING MEMBER, A DISCHARGE PASSAGEIN SAID HOUSING ADAPTED TO BE CONNECTED TO THE CYLINDER DEVICE DISCHARGEPORT TO RECEIVE DISCHARGE FLUID FROM THE DEVICE, A VALVE SEAT IN SAIDPASSAGE, A VALVE MEMBER IN SAID PASSAGE POSITIONED TO CLOSE INOPPOSITION TO THE PRESSURE OF THE DISCHARGE FLUID SO THAT DISCHARGEFLUID TENDS TO OPEN SAID VALVE MEMBER, A LOW PRESSURE RETURN PASSAGE INSAID VALVE HOUSING SELECTIVELY CONNECTABLE WITH SAID DISCHARGE PASSAGETHROUGH SAID VALVE MEMBER, RESILIENT MEANS FOR BIASING SAID VALVE MEMBERTO A CLOSED POSITION, SAID RESILIENT MEANS BEING OF SUFFICIENT STRENGTHTO MAINTAIN SAID VALVE MEMBER CLOSED AGAINST THE PRESSURE OF THEDISCHARGE FLUID IN SAID DISCHARGE PASSAGE, SAID VALVE SEAT LIMITINGMOVEMENT OF SAID VALVE MEMBER BEYOND SAID CLOSED POSITION, CONTROL MEANSFOR SELECTIVELY OPENING SAID VALVE MEMBER AND PERMITTING DISCHARGE FLOWFROM SAID DISCHARGE PASSAGE TO SAID RETURN PASSAGE INCLUDING FLUIDACTUATED MEANS SEPARATE FROM SAID DISCHARGE PASSAGE CONNECTED TO OPENSAID VALVE MEMBER WHEREBY DISCHARGE FLUID LEAKAGE IS MINIMIZED ANDBYPASS PASSAGE MEANS IN PARALLEL WITH SAID VALVE MEMBER COMMUNICATINGWITH SAID LOW PRESSURE RETURN PASSAGE AND SAID DISCHARGE PASSAGE FORSUPPLY FLUID UNDER PRESSURE TO THE DISCHARGE PORT OF THE DEVICE.